Add optional 'author' param when making commits

This fulfills https://gitlab.com/gitlab-org/gitlab-ce/issues/20789 by adding the ability to specify a user's ID to be used as the author of a commit.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/20789

See merge request !5822

LFS support for ssh enabled

## What does this MR do?
This is follow-up after https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6043 which is falsely shown as merged due to: https://gitlab.com/gitlab-org/gitlab-ce/issues/22334

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

See merge request !6413

Ensure invitees are not returned in Members API

## What are the relevant issue numbers?

Closes #22065

See merge request !6370

Allow to set request_access_enabled for groups and projects using API

Closes #20978

See merge request !6359

This reverts commit 6d43c95b7011ec7ec4600e00bdc8df76bb39813c.